Pws Mk118 Mod 1-M Upper 6Arc 18 Ls Threaded

The Primary Weapons Systems Mk118 Mod 1-M upper receiver in 6 ARC brings a modern intermediate cartridge platform to builders and shooters looking for a refined semi-custom AR experience. Built on the Mk118 chassis—PWS's proven fighting rifle foundation—this upper pairs 6 ARC's ballistic efficiency with an 18-inch barrel and a threaded muzzle, giving you the flexibility to add a suppressor, muzzle brake, or flash hider to suit your mission. Whether you're running this as a precision rifle build, a mid-range hunting rig, or a modular training platform, the Mk118 Mod 1-M delivers the accuracy and consistency PWS is known for without the premium pricing of a complete rifle.

6 ARC has earned respect in the long-range and precision communities for its flatter trajectory and superior wind drift performance compared to 5.56 NATO, yet it remains easy on brass and ammunition costs relative to larger magnum calibers. The 18-inch barrel length gives you velocity gains over 16-inch alternatives while keeping the overall profile manageable for tactical use or field hunting. A threaded muzzle is already in place, so you can run suppressed right out of the box if you choose—a practical feature for shooters looking to reduce noise signature on the range or in the field.

This is an upper receiver assembly, designed to mate with a compatible lower receiver to complete your rifle build. If you already run PWS or standard AR architecture, you know what to expect: tight tolerances, reliable function, and honest engineering without the marketing fluff.

Key Features

• 6 ARC chambering—ballistically superior intermediate round with excellent long-range performance
• 18-inch barrel for optimized velocity and accuracy balance
• Threaded muzzle ready for suppressor or brake installation
• Mk118 Mod 1-M proven PWS upper platform
• Upper receiver assembly (lower receiver required to complete rifle)

Frequently Asked Questions

What lower receiver does this upper pair with?

This is a standard AR platform upper receiver. It will mate with any compatible AR-15 lower receiver following proper assembly procedures. Consult the manufacturer if you have questions about compatibility with your specific lower.

Can I add a suppressor to the threaded muzzle?

Yes. The upper comes with a threaded muzzle, so you can install a suppressor, muzzle brake, or flash hider that matches the thread pattern. Confirm the thread pitch with PWS specifications before purchasing a muzzle device.

Is 6 ARC good for hunting?

6 ARC has gained a following among precision-minded hunters and long-range shooters for its flat trajectory and wind handling. Suitability depends on your game and intended distance—consult local regulations and consider your shot placement capability.

What does "upper receiver assembly" mean?

An upper receiver is the serialized or non-serialized top half of an AR rifle. This upper includes the barrel, bolt carrier group, and operating system. You'll need to pair it with a lower receiver (the fire control group half) and assemble them to have a complete, functional rifle.